Bass River Coastal Hydraulic Study

Dennis-Yarmouth, Massachusetts

The Cape Cod Rail Trail extension will cross Bass River at the site of the most restrictive hydraulic opening on the tidal river, which features restricted tidal exchange and boat navigation hazards. VHB led the hydraulic analysis to evaluate four alternative pedestrian bridge designs, developing an unsteady-state model using HEC-RAS software to simulate tidal flushing and identify hydraulically viable abutment alternatives. VHB used the model to evaluate alternative larger bridge openings, assessing benefits to tidal exchange and navigation and potential impacts to flood levels during extreme events. The preferred alternative, under design, will increase tidal flushing of the river system and improve navigation.